Cerithium caeruleum, the Cerith sand snail, is a species of sea snail, a marine gastropod mollusk in the family Cerithiidae. Cerithium caeruleum, also be called Cerithium caeruleum G.B. Sowerby II, 1855 generally can be found in large populations on intertidal rocky shores and are covered by a thin layer of sediments. They have large and solid shells, and their radula ribbon robust long about one-fifth the shell length. This species lives in the planktonic stage from 90 to 120 days and has a seven-year life history. This common intertidal species is confined to east Africa, Madagascar, and the Arabian Peninsula and is unlikely to be confused with any other Cerithium species. It is distinguished by its squat, knobby shape; and as indicated by its name, caeruleum, a grayish blue color with spiral rows of black tubercles. Description 1. Shell This species is widespread in the tropical Indo-Pacific (Red Sea, Kenya, Madagascar, Mozambique, Tanzania and Western India). The shell of Cerithium caeruleum is large, solid, stocky, knobby, reaching 41.5 mm length and 19.2 mm width, and comprising 8-12 angulate, nodulose whorls. Early teleoconch whorls sculptured with 2 or 3 spiral cords, numerous fine spiral lirae, and weak axial ribs. Adult teleoconch whorls angulate, sculptured with numerous spiral lirae separated by incised spiral lines, fine, colabral axial lines, and with two dominant spiral cords— small, beaded, belt-like, subsutural cord, and very large, nodulose, median cord. A median spiral cord of penultimate whorl has 8-12 large nodes and a wide sutural ramp. Nodes are sometimes spiny and axially drawn out. The suture is slightly impressed. Body whorl large, wide, elongate, with weak siphonal constriction. Body whorl microsculpture same as on adult whorls, but with 4 or 5 major nodulose, beaded, or nearly smooth, spiral cords. The aperture is ovate, a little more than one-third the shell length. Columella concave with moderate thick callus. Anterior siphonal canal is short and strongly reflected left of shell axis. Anal canal is deep and folded into weak inner denticles. Shell color grayish-blue flecked with white; nodes black, early whorls white. 2. Radula Radular ribbon is robust, long, about one-fifth the shell length. Rachidian tooth is squarish; basal plate is with pair of posterior lunule-shaped ridges and weak, central, posterior projection. Cutting edge of rachidian has large, triangular, pointed main cusp, flanked on either side by two, sometimes three, blunt, very small denticles. The Lateral tooth has basal